In particular, the present invention relates to a plant for producing, conveying and packaging rolls of strip-like material wound on a support core, for instance in the form of rolls of paper material or the like destined to domestic or similar use, wound on a cardboard core tube. Such rolls are preferably rolls of toilet paper, kitchen paper, aluminum foil and other materials destined to personal, domestic, industrial use or the like.
In general, known plants for producing and packaging said rolls comprise, upstream, an apparatus for forming the rolls having a shearing machine that cuts said rolls from respective logs or coils which are cut simultaneously in a predefined number, for instance equal to 2, 3 or 4, and sent onto parallel conveying lines towards respective packaging machines.
Known machines for forming the rolls further comprise a series of operative sections which produce said coils or logs, wherefrom said rolls are cut off, starting from a main coil for feeding the paper material or the like. Said feeding coil is large in size and it is obtained directly from the plant that produces this material, generally from the paper mill. Known forming machines thus comprise an initial coil loading section, which generally supports at least a first and a second said feeding coils, to allow for a continuous feeding of the roll producing apparatus, and which unwinds the paper strip from the feeding coil and transfers it to a successive section in which the paper is embossed to increase the volume of said paper strip. Downstream of the embossing section, several layers of said paper may be coupled and a re-coiling section is present which receives the core tubes from an appropriate section dedicated to their forming, whereon it glues and winds a quantity of paper of a diameter corresponding to that of the rolls to be produced, obtaining the logs or elongated coils to be cut into rolls. Such logs or elongated coils are then sent to a successive section for storing said logs or elongated coils and, thence, to the section for cutting the rolls off from said logs.
In known plants, the upstream shearing machines performs the transverse cutting of said rolls from logs or elongated coils, whose length is a multiple of the length of the individual roll to be cut, and one or more downstream packaging machines package said rolls in appropriate packs, made with a coating film of plastic or paper material, which contain a pre-selected number of said articles, ordered in rows which may be arranged in multiple layers.
Said packaging machines provide a certain number of types of packages of articles, each having predetermined dimensions and being composed by a pre-defined number of rolls, arranged according to a pre-set configuration. Moreover, each type of pack is also distinguished in relation to the type of roll (geometric dimensions) and type of paper used to form said rolls.
Each customer of the plant who purchases the packaged rolls generally requires a respective type of package. Plants for producing said rolls provide a series of successive production runs, possibly destined to different customers, in which packages and corresponding rolls with mutually different characteristics are manufactured.
Known plants normally make use of a shearing machine with high productive rates, whereto is associated more than one machine for packaging the rolls, each generally operating at a lower speed than the working speed of the shearing machines.
In known plants, the roll forming and packaging machines generally differ from each other, are produced by different manufacturers and thus have wholly differentiated operating performance.
Plants where the material in rolls is produced and packaged generally use machines made by different manufacturers. This occurs, for instance, because said machines were acquired at different times, or because said machines are selected according to specific advantageous characteristics which they present.
In plants according to the prior art and in particular in plants that employ machines produced by different manufacturers, however, there is a problem with coordinating the operation between the roll forming machines and the packaging machines, as well as between the packaging machines and the conveyor belts connecting them, which causes the actual yield of the production plants to be quite low and does not allow sufficiently to exploit the high working rate potential of the aforesaid known machines.
Currently, in the present field, packaging machines present their own control unit or PLC, which autonomously controls, through an appropriate software program, the extremely complex and articulated operation of this type of machine. In particular, this PLC allows to set, among other parameters, the working rate of said machine, which is normally set equal to the maximum working rate that can be obtained from said machines, for the purpose of exploiting its potential to the utmost.
In such traditional plants, the settings of the operation, in particular of the working rate, of the different cutting and packaging machines and of the conveying apparatus, for instance every time the operation must be adapted to the changed format of the roll packs to be produced—i.e. to the number and disposition of the articles to be packaged in a single pack—are conducted independently for each individual machine, by assigned operators, who make use of respective keyboards for entering data into the respective PLC's or local control units of the aforesaid machines.
Such a way of proceeding, which entails an adjustment of the system that could be defined of the “manual” kind, is, however, quite unproductive. It is not at all easy for the operators, who generally do not have a very high education level, to obtain a proper adjustment of the system, especially when it is necessary to manage several format changes and the operators of the various machines have difficulties communicating with each other. This also takes place in consideration of the fact that the plants present considerable dimensions and there is an objective difficulty in communicating, also because of the noise in the plants, and in moving between the densely spaced lines for conveying the articles.
Such a local adjustment of the operation of each individual machine in the system usually leads to an incorrect operation of the system. Known plants, to overcome these less than correct adjustments of the system, make use of normal automatic controls for stopping system operation, which are activated through signals provided by optical sensors of maximum and minimum load in correspondence with the working machines. It may occur, when said packaging machines are fed an excessive number of articles, an automatic signal is emitted to command the upstream cutting machine to stop, while a corresponding signal to stop the packaging machine itself is emitted when said machines are fed an insufficient quantity of articles. In known plants, therefore, a fluctuating type of operation takes place, with working phases alternating with idle phases, of the different machines in the plant. Therefore, even in the presence of machines that are able to operate at high speeds, one actually obtains rather modest production rates, which frustrate the heavy financial investment needed to purchase such high speed machines.
Moreover, this way of operating, which ultimately entails numerous stops of the upstream shearing or forming machine, as well as of the packaging machine, is quite harmful to the duration of their working life. The components of said machines are subjected to continuous accelerations and decelerations needed to bring them from the operating condition to the stopped condition, which induce stresses that, in the long term, lead to failures and wear of the main mechanical parts of the machines. The forming shearing machines comprise, for instance, an ample circular blade which, with a single movement in a plane transverse to the elongated logs, simultaneously cuts multiple rolls, in particular a number of rolls equal to the number of logs fed in correspondence with said cutting blade. The stops, due to emergency causes, of said circular blade, can, over time, damage the actuating mechanism of the blade, with considerable repair costs and production losses due to the machine idle time.
In traditional plants for articles, such as said rolls, the risk that the articles may be upset is high and the consequent plant stop causes production losses and, over time, the failure and wear of the mechanical parts of the parts employed. The number of upsets that take place is influenced by the velocity of conveyance of the articles and by the format of the rolls. Obviously, for short rolls with large diameters the risk of upsetting is greater. Therefore, making the upstream shearing machine operate at the maximum working rate aggravates the risk of upsetting the articles, at least in relation to certain types of products, such as the aforesaid rolls with reduced length.
It should also be noted that, in known plants, rolls can be damaged, during their transfer, by excessively high conveyance speeds, especially due to the contact of the rolls themselves with the conveying guides.
Also known are plants for forming articles and packaging them in corresponding packs. For instance, the prior document EP-A-0654408, discloses an apparatus for feeding products on a single row from a single manufacturing machine positioned upstream of two packaging machines positioned downstream, in which, to transfer the products from a continuous conveyor belt exiting the machine that manufactures the products to a first and a second conveyor for respective packaging machines, use is made of a translator which alternatively and individually moves the products respectively onto the first and onto the second conveyor of the respective packaging machine.
A central microprocessor unit directly controls the units commanding the respective electric motors for the actuation of the packaging machines. Said central control unit also acts directly on the control boards of the individual electric motors for actuating the production machine and of the electric motor that controls the conveyor exiting the production machine.
As described in document EP-A-0654408, the production machine is made to operate, under normal conditions, at the maximum working rate, whilst the packaging machines are made to operate at a lesser working rate than their respective maximum level.
According to the description provided in document EP-A-0654408, if one of the packaging machine stops operating due to an emergency, the working rate of the still active packaging machine is increased and, simultaneously, the working rate of the production machine is slowed.
Therefore, this is a complete plant destined to be marketed as a whole, not designed to be inserted in existing plants or to co-operate with different machines already present in the production plant.
The operating philosophy whereon the device described in this prior document EP-A-0654408 is based, it is that of obtaining large production runs by making the machine that forms the articles run at its top working rate. This plant has no provision for the initial setting of the working rate of the individual machine according to other operating modes which may vary according to the characteristics of the product to be handled.